Various means have been used in the prior art to removably attach a round having a tail fin assembly to a combustible cartridge case so that both items could be simultaneously loaded into a launching weapon. In the prior art these two members were joined together by a threaded joint. The problem with this prior art construction was that the threaded assembly would not pass a United States MIL-STD 311, Test No. 111, standard drop test criteria. In addition, not only did the prior art fail the drop test, but the threads in the polypropylene cartridge case attachment had to be made oversize to provide sufficient retention of the projectile during initial loading placed upon it by the ignited propellant. As a result of the use of an oversize thread for the cartridge case attachment many parts were vulnerable to damage during assembly of the cartridge case attachment to the projectile, and as a result of this damage many parts had to be rejected.